1. Field of the Invention
The present invention relates to valves for controlling fluid flow in an internal combustion engine. More particularly, the present invention relates to reed valves for controlling intake and/or transfer fluid flow in such engines.
2. Background of the Prior Art
Reed valves are presently widely employed in internal combustion engines to control air or air/fuel intake. In two-stroke cycle engines, such as disclosed in U.S. Pat. Nos. 3,905,340, 3,905,341, and 4,051,820, such reed valves play an important role in supporting the improved operation of the engine and the proper transfer of air and fuel from crankcase to combustion chamber. More recently, such reed valves also have been employed in four-stroke cycle engines to control air intake and improve engine performance.
In U.S. Pat. No. 3,905,340 it is disclosed that significant improvements in reed valve life and performance may be achieved by substituting a multiple stage reed valve design in place of a conventional single stage reed. In the design disclosed in that patent, a relatively stiff primary reed is utilized having ports therein. A secondary reed member is then oriented over the ports in the primary reed, with a secondary reed petal sealing each of the primary reed ports. The secondary reed member provides fluid flow through the ports in the primary reed member. In order to allow such flow, the secondary reed members are far more flexible than the primary reed so that the secondary reed member opens farther than the primary reed during the pressure changes each engine cycle. The invention of the '340 patent improves engine performance in virtually all applications and, due to the reduced stresses inherent with this design, reed valve life is dramatically increased.
Although the multi-stage reed disclosed in U.S. Pat. No. 3,905,340 functions very well, it has been found that further improvements may be possible to that design. One problem that has been encountered is that many intake passages have uneven flow distribution through them which results in greater stress placed on certain petals of the secondary reed. As a result of the increased stresses placed on only some of the reed petals, the over-stressed petals will undergo material fatigue and break far more rapidly than less stressed reed petals. Applicant's U.S. Pat. No. 4,696,263 attempts to address this problem in part by providing a protective coating of synthetic rubber on the reed valves to prolong their life.
Further, uneven flow distribution through the air intake, conventional or multi-staged reeds do not provide optimum air intake distribution into the engine. One solution to this problem is addressed in applicant's U.S. Pat. No. 4,879,976 for an aeroform reed valve cage which modifies the intake passage upstream from the reed valves so to provide more even air flow through the reed valves. Another approach to solving this problem is disclosed in U.S. patent application Ser. No. 465,472, now allowed, which calls for joining together the reed petals of the secondary reed member to improve intake flow and reduce reed petal fatigue.
Notwihhstanding these advances, additional improvements in reed valve performance and life are shown to be possible. First, even though it is known that thicker reed material has a significantly better operating life, the thickness of the reed valves is necessarily limited by the need to assure proper reed flexibility to allow the valves to have proper frequency response.
Another major problem that still exists is that all the above multiple stage reeds are dependent upon use of relatively narrow primary reed ports and corresponding petals. Although wider ports may improve fluid intake, wider petals have been avoided because they are subject to greater strain and fatigue. It is known that wider petals are stressed or destroyed when they flex into and/or "blow-through" wider ports under heavy pressure modes during certain stages of the operation of an engine.
The impact of this problem is also evident in reed cage designs which have traditionally included narrow segmented openings to help support each of the individual reed petals. Despite efforts to create aerodynamic supports, these supports necessarily add to turbulence and disruption of proper fluid intake. Although the problem of turbulence from these supports is addressed by advancements in the aerodynamics of reed cage design, such as the reed cages disclosed in U.S. Pat. No. 4,879,976, the continued existence of segments between the numerous narrow ports in primary reed members tend to limit the advantages of such technology.
Accordingly, it is a primary object of the present invention to provide an improved reed valve which provides all the benefits of prior multi-stage reed valves while having improved flow characteristics, improved performance, and further increased operating life.
It is a further object of the present invention to provide a reed valve with the above advantages which employs thicker reed valve material and wider reed valve ports and petals for improved life and flow characteristics.
It is another object of the present invention to provide a reed valve with the above advantages which better complements advancements in aerodynamic reed cage technology.
It is a additional object of the present invention to provide a reed valve with the above advantages which is straightforward in design and adds no weight, complexity, or expense to the engine or the air intake system.
These and other objects of the present invention will become evident from review of the following specification.